refactor: slightly simplify checkout logic

common/src/main/java/net/william278/husksync/sync/LockstepDataSyncer.java

@@ -45,15 +45,15 @@ public class LockstepDataSyncer extends DataSyncer {
     @Override
     public void setUserData(@NotNull OnlineUser user) {
         this.listenForRedisData(user, () -> {
-            if (getRedis().getUserCheckedOut(user).isEmpty()) {
+            if (getRedis().getUserCheckedOut(user).isPresent()) {
+                return false;
+            }
             getRedis().setUserCheckedOut(user, true);
             getRedis().getUserData(user).ifPresentOrElse(
                     data -> user.applySnapshot(data, DataSnapshot.UpdateCause.SYNCHRONIZED),
                     () -> this.setUserFromDatabase(user)
             );
             return true;
-            }
-            return false;
         });
     }
 

common/src/main/java/net/william278/husksync/user/OnlineUser.java

@@ -125,7 +125,7 @@ public abstract class OnlineUser extends User implements CommandUser, UserDataHo
         getPlugin().fireEvent(getPlugin().getPreSyncEvent(this, snapshot), (event) -> {
             if (!isOffline()) {
                 getPlugin().debug(String.format("Applying snapshot (%s) to %s (cause: %s)",
-                        snapshot.getShortId(), getUsername(), cause
+                        snapshot.getShortId(), getUsername(), cause.getDisplayName()
                 ));
                 UserDataHolder.super.applySnapshot(
                         event.getData(), (succeeded) -> completeSync(succeeded, cause, getPlugin())